This invention relates to a fuel supply and distribution system and, more particularly, to a fuel supply and distribution system for a gas turbine engine wherein a plurality of flow dividing valves are positively actuated in a manner which precludes sticking or seizure on account of contaminant particulate matter in the fuel.
In a gas turbine engine, fuel is generally supplied to a combustor by a plurality of fuel injectors which receive a regulated flow of fuel from an inter-connecting manifold. Between the manifold and each fuel injector, there is generally provided a flow dividing valve which operates to establish a minimum pressure within the manifold before fuel will initially flow to the injectors. After fuel flow is initiated through the injectors, each flow dividing valve operates to maintain the same flow versus pressure drop characteristic. Thus the flow dividing valves insure that each fuel injector receives the same rate of fuel flow in order to uniformly distribute fuel around the engine combustor.
The flow dividing valves are generally relief valves with the same flow versus pressure drop characteristic wherein each valve has a precise metering window which cooperates with a spring actuated metering piston to accurately schedule fuel flow for a particular pressure drop. Because of the close diametral fit of the metering piston (normally 0.0005 inch or less), this type of valve is highly susceptible to sticking or seizure due to contaminant particulate matter in the fuel lodging between the moving valve surfaces.
Because of the small size of the contaminant particulate matter which can cause the valve to stick, any filter suitable to block such contaminants would either incur too great a pressure drop or would be too large in size to be practical. Thus replacement of such valves due to sticking has become a common field complaint. Military specifications also now require all fuel system components to be able to pass a contaminated fuel test.
Therefore it is a primary object of this invention to provide a fuel supply and distribution system which can pass contaminated fuel without valves sticking or seizing.
It is also an object of this invention to provide a fuel supply and distribution system for a gas turbine engine wherein a plurality of flow dividing valves are positively actuated in a manner which precludes sticking or seizure on account of contaminant particulate matter in the fuel.